Wireless communication handover responsive to uplink interference at a serving cell

ABSTRACT

A wireless communication network hands-over wireless User Equipment (UE) from a serving cell to a neighbor cell. The serving cell wirelessly exchanges data with the wireless UE and determines uplink interference for a radio band. The serving cell wirelessly transfers an uplink interference offset to the wireless UE that indicates the uplink interference at the serving cell for the radio band. The wireless UE uses the uplink interference offset to trigger a handover request to the serving cell. The handover request indicates downlink signal strength at the wireless UE for the serving cell. The serving cell initiates a handover to a neighbor cell responsive to a combination of the downlink signal strength at the wireless UE and the uplink interference for the serving cell falling below a handover threshold. After the handover, the neighbor cell wirelessly exchanges data with the wireless UE over a different radio band.

TECHNICAL BACKGROUND

Wireless communication networks provide wireless data services towireless user devices. The wireless data services includeinternet-access, media-streaming, machine communications, and the like.Exemplary wireless user devices comprise phones, computers, wearabletransceivers, vehicles, robots, and sensors. The wireless communicationnetworks have wireless cells that exchange wireless signals with thewireless user devices over Radio Frequency (RF) bands using wirelessnetwork protocols. Exemplary wireless network protocols includeInstitute of Electrical and Electronic Engineers (IEEE) 802.11 (WIFI),Long Term Evolution (LTE), Fifth Generation New Radio (5GNR), andLow-Power Wide Area Network (LP-WAN).

To enable user mobility for the wireless data services, the wirelesscommunication networks handover the wireless user devices among thewireless cells as the wireless user devices move about. In a typicaldevice handover, a serving cell hands-over the wireless user device to atarget cell as the wireless user device moves away from the serving celland toward the target cell. To initiate the handover, the wireless userdevice detects when the downlink signal strength from the serving cellfalls below a serving threshold and when the downlink signal strengthfor the target cell rises above a target threshold. In addition to thesignal strength values, the wireless user device also uses hysteresisvalues to mitigate ping-pong effects during the handover.

When assessing the target cell signal, the wireless user device usesoffsets in combination with the signal strength and hysteresis values.The offsets indicate a cell-specific value and a frequency-specificvalue for the target cell. The downlink signal strength defines downlinkradio coverage, and the downlink radio coverage may be larger than theuplink radio coverage. The target cell offsets adjust the downlinksignal strength value to better correspond to the smaller uplink radiocoverage. The smaller uplink radio coverage causes problems for wirelessuser devices at the cell edge that have a downlink but no uplink. Uplinkinterference causes sudden and significant uplink coverage loss but maynot shrink downlink coverage by the same magnitude.

The uplink/downlink coverage mismatch problem is exacerbated by the useof multiple frequency bands. On an inter-band handover from a servingfrequency band to a target frequency band, the serving cell andfrequency band may experience significant uplink coverage loss, whilethe target cell and frequency band do not exhibit uplink coverage loss.Unfortunately, the wireless user device and the serving cell do notefficiently and effectively process uplink interference at the servingcell during inter-band handovers.

Technical Overview

A wireless communication network hands-over wireless User Equipment (UE)from a serving cell to a neighbor cell. The serving cell wirelesslyexchanges data with the wireless UE and determines uplink interferenceover a radio band. The serving cell wirelessly transfers an uplinkinterference offset to the wireless UE that indicates the uplinkinterference at the serving cell for the radio band. The wireless UEuses the uplink interference offset to trigger a handover request to theserving cell. The handover request indicates downlink signal strength atthe wireless UE for the serving cell. The serving cell initiates ahandover to a neighbor cell responsive to a combination of the downlinksignal strength at the wireless UE and the uplink interference for theserving cell falling below a handover threshold. After the handover, theneighbor cell wirelessly exchanges data with the wireless UE over adifferent radio band.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication network to handover wirelessUser Equipment (UE) in response to Uplink (UL) interference at a servingcell.

FIG. 2 illustrates the operation of the wireless communication networkto handover the wireless UE in response to the UL interference at theserving cell.

FIG. 3 illustrates the operation of the wireless communication networkto handover the wireless UE in response to the UL interference at theserving cell.

FIG. 4 illustrates a UE that triggers a handover in response to ULinterference.

FIG. 5 illustrates an Evolved Universal Terrestrial Radio Access NetworkDirect Connectivity (EN-DC) access node that hands-over the wireless UEin response to the UL interference.

FIG. 6 illustrates a Network Function Virtualization Infrastructure(NFVI) to support the handover of the UE in response to the ULinterference.

FIG. 7 illustrates the operation of an EN-DC communication network tohandover a wireless UE in response to the UL interference.

DETAILED DESCRIPTION

FIG. 1 illustrates wireless communication network 100 to handoverwireless User Equipment (UE) 101 in response to Uplink (UL) interferenceat serving cell 111. Wireless communication network 100 supportswireless data services like internet-access, media-streaming, messaging,gaming, machine-communications, and/or some other wireless data product.Wireless communication network 100 comprises wireless UE 101, servingcell 111, neighbor cell 112, and network elements 121.

Before the handover, wireless UE 101 and serving cell 111 are coupledover Radio Frequency (RF) band 131. After the handover, wireless UE 101and neighbor cell 112 are coupled over RF band 132. RF bands 131-132 usedifferent frequency blocks and do not share electromagnetic spectrum.Thus, the handover represents an inter-band handover for wireless UE 101between RF bands 131-132. RF bands 131-132 use frequency blocks in thelow-band, mid-band, high-band, or some other part or the wirelesselectromagnetic spectrum. RF bands 131-132 transport wirelesscommunication protocols like Fifth Generation New Radio (5GNR), LongTerm Evolution (LTE), Low-Power Wide Area Network (LP-WAN), Institute ofElectrical and Electronic Engineers (IEEE) 802.11 (WIFI), or some otherwireless networking protocol.

Serving cell 111 and neighbor cell 112 are coupled to one another overbackhaul links 141. Serving cell 111 and neighbor cell 112 are alsocoupled to network elements 121 over backhaul links 141. Backhaul links141 may use Time Division Multiplex (TDM), IEEE 802.3 (ETHERNET),Internet Protocol (IP), Data Over Cable System Interface Specification(DOCSIS), LTE, 5GNR, virtual switching, radio tunneling protocols, orsome other data network protocol.

Wireless UE 101 might be a phone, computer, wearable transceiver, robot,vehicle, or some other data appliance with wireless communicationcircuitry. Wireless UE 101 comprises radios and user circuitry which arecoupled over bus circuitry. The radios comprise antennas, filters,amplifiers, analog-to-digital interfaces, microprocessors, memory,software, transceivers, bus circuitry, and the like. The user circuitrycomprises microprocessors, memory, software, transceivers, buscircuitry, and the like. The microprocessors comprise Digital SignalProcessors (DSP), Central Processing Units (CPUs), Graphical ProcessingUnits (GPUs), Application-Specific Integrated Circuits (ASICs), and/orthe like. The memories comprise Random Access Memory (RAM), flashcircuitry, disk drives, and/or the like. The memories store softwarelike operating systems, user applications, and network applications.

Serving cell 111 and neighbor cell 112 comprise radios and BasebandUnits (BBUs) which are coupled over bus circuitry. The radios compriseantennas, filters, amplifiers, analog-to-digital interfaces,microprocessors, memory, software, transceivers, bus circuitry, and thelike. The BBUs comprise microprocessors, memory, software, transceivers,bus circuitry, and the like. The microprocessors comprise DSP, CPUs,GPUs, ASICs, and/or the like. The memories comprise RAM, flashcircuitry, disk drives, and/or the like. The memories store softwarelike operating systems and network applications. In some examples, cells111-112 comprise Evolved Universal Terrestrial Radio Access NetworkDirect Connectivity (EN-DC) access nodes that use 5GNR and LTE.

Network elements 122 comprise microprocessors, memory, software, and businterfaces. The microprocessors comprise CPU, GPU, ASIC, and/or thelike. The memory comprises RAM, flash circuitry, disk drive, and/or thelike. The memory stores software like operating system and networkapplications. Exemplary network elements 122 include Access and MobilityManagement Functions (AMFs), Session Management Functions (SMFs),Mobility Management Entities (MMEs), User Plane Functions (UPFs),Serving Gateways (SGWs), Packet Data Network Gateways (PGWs), and/or thelike. In some examples, network elements 121 comprise Virtual NetworkFunctions (VNFs) in a Network Function Virtualization Infrastructure(NFVI).

Before the handover of wireless UE 101 from serving cell 111 to neighborcell 112, serving cell 111 wirelessly exchanges data with wireless UE101 over RF band 131. Serving cell 111 determines the UL interferencefor RF band 131 at serving cell 111. The UL interference comprisesunwanted energy in RF Band 131 that is typically caused by the wirelessUEs and their serving cells. The UL interference does not typicallyinclude signal energy or noise energy, although any measure that variesin relation to UL interference could be used.

Serving cell 111 wirelessly transfers an UL interference offset towireless UE 101 that indicates the uplink interference for RF band 131at serving cell 111. Serving cell 111 usually transfers additionaloffsets to wireless UE 101 as well. The UL interference offset forserving cell 111 may comprise a measurement object specific offset forserving cell 111. The UL interference offset accelerates handovers whenUL interference is high at serving cell 111 and decelerates handoverswhen UL interference is low at serving cell 111.

Wireless UE 101 determines Downlink (DL) signal strength at wireless UE101 for serving cell 111. Wireless UE 101 also determines DL signalstrength at UE 101 for neighbor cell 112. Wireless UE 101 uses the ULinterference offset and the DL signal strengths to trigger a handoverrequest to serving cell 111. For example, UE 101 may compare data forserving cell 111 (UL interference, DL signal strength, hysteresis value)to a serving threshold, and when the combination falls below the servingthreshold, UE 101 compares data for neighbor cells (DL signal strength,neighbor cell offset, neighbor frequency offset, hysteresis value) to atarget threshold. When the data for serving cell 111 falls below theserving threshold, and the data for neighbor cell 112 rises above thetarget threshold, UE 101 transfers a handover request to serving cell111 that indicates the DL signal strength at UE 101 for cells 111-112(and typically data for other neighbor cells).

Serving cell 111 receives the handover request from wireless UE 101 thatindicates the DL signal strengths for cells 111-112. Serving cell 111initiates the handover to neighbor cell 112 responsive to the DL signalstrengths, UL interference, and typically other offsets and hysteresisvalues. After the handover, neighbor cell 112 wirelessly exchanges datawith the wireless UE 101 over RF band 132.

In some examples, the serving threshold comprises an A5-1 inter-bandhandover threshold, and the target threshold comprises an A5-2inter-band handover threshold. In some examples, the neighbor frequencyoffset (or neighbor cell offset) is based at least in part on thehistorical uplink interference at neighbor cell 112 on RF band 132 forthe current day, date, and time. The neighbor frequency offset (or celloffset) that indicates the neighbor UL interference may comprise ameasurement object specific offset for neighbor cell 112.

FIG. 2 illustrates the operation of wireless communication network 100to handover wireless UE 101 in response to UL interference at servingcell 111 over RF band 131. Before the handover, wireless UE 101 andserving cell 111 wirelessly exchange data over RF band 131 (201).Serving cell 111 determines the UL interference for RF band 131 atserving cell 111 (202). Serving cell 111 wirelessly transfers an ULinterference offset to wireless UE 101 that indicates the uplinkinterference (203). Wireless UE 101 determines Downlink (DL) signalstrength at wireless UE 101 for serving cell 111 and neighbor cell 112(204). Wireless UE 101 determines when a combination of the DL signalstrength and UL interference for serving cell 111 falls below a first UEthreshold—UE TH1 (205). Wireless UE 101 also determines when acombination of DL signal strength and offsets for neighbor cell 112rises above a second UE threshold—UE TH2 (205). When both thecombination of the DL signal strength and UL interference for servingcell 111 falls below the first UE threshold and the combination of theDL signal strength and neighbor offsets for neighbor cell 112 risesabove the second UE threshold (206), wireless UE 101 transfers ahandover request to serving cell 111 with the DL signal strength at UE101 for serving cell 111 and neighbor cell 112 (207).

Serving cell 111 determines when a combination of the DL signal strengthand UL interference for serving cell 111 falls below a first networkthreshold—NET TH1 (208). Serving cell 208 also determines when acombination of DL signal strength and neighbor offsets for neighbor cell112 rises above a second network threshold—NET TH2 (208). When thecombination of the DL signal strength and UL interference for servingcell 111 falls below the first NET threshold, and the combination of theDL signal strength and neighbor offsets for neighbor cell 112 risesabove the second NET threshold (209), serving cell 111 initiates thehandover for UE 101 to neighbor cell 112 (210). After the handover,neighbor cell 112 wirelessly exchanges data with the wireless UE 101over RF band 132 (211). The process then repeats (202) with neighborcell 112 being the new serving cell and serving cell 111 being a newneighbor cell.

FIG. 3 illustrates the operation of wireless communication network 100to handover wireless UE 101 in response to the UL interference atserving cell 111. Wireless UE 101 and serving cell 111 wirelesslyexchange data over RF band 131. Serving cell 111 and network elements121 exchange the data. Network elements 121 and other data systemsexchange the data. Serving cell 111 determines UL interference andwirelessly transfers offsets to wireless UE 101. One of the offsetsindicates the recently-determined UL interference at serving cell 111.Wireless UE 101 determines DL signal strength at UE 101 for serving cell111 and neighbor cell 112. Wireless UE 101 detects an inter-frequencyhandover trigger by using the DL signal strength at UE 101 for cells111-112 and the offsets—including the UL interference offset for servingcell 111. Hysteresis values may also be used. In response to theinter-frequency handover trigger, wireless UE 101 transfers a handoverrequest to serving cell 111 that indicates the DL signal strength at UE101 for serving cell 111 and neighbor cell 112.

Serving cell 111 initiates a handover for UE 101 to neighbor cell 112based on the signal strengths and the offsets—including UL interferencefor serving cell 111. To perform the handover, serving cell 111exchanges handover signaling with neighbor cell 112, UE 101, and networkelements 121. Neighbor cell 111 then exchanges handover signaling withUE 101 and network elements 121. In response to the handover signaling,wireless UE 101 and neighbor cell 112 wirelessly exchange data over RFband 132. Neighbor cell 112 and network elements 121 exchange the data,and network elements 121 exchange the data with other data systems.

Advantageously, serving cell 111 and UE 101 efficiently use uplinkinterference at serving cell 111 when triggering an inter-band handoverto neighbor cell 112. UE 101 effectively escapes bad UL coverage atserving cell 111 to obtain better UL coverage at neighbor cell 112. UE101 also improves DL signal strength through the handover from servingcell 111 to neighbor cell 112.

FIG. 4 illustrates wireless UE 401 that triggers a handover in responseto UL interference at serving Evolved Universal Terrestrial Radio AccessNetwork Direct Connectivity (EN-DC) access node 411 in EN-DCcommunication network 400. UE 401 is an example of wireless UE 101,although UE 101 may differ. EN-DC communication network 400 comprises UE401, EN-DC access node 411, and Network Function VirtualizationInfrastructure (NFVI) 420. NFVI 420 includes Mobility Management Entity(MME) 421 and System Evolution Architecture (SAE) Gateway (GW) 422.

UE 401 comprises 5GNR radios 402, LTE radios 403, and user circuitry 404which are interconnected over bus circuitry. Radios 402-403 compriseantennas, amplifiers, filters, modulation, analog-to-digital interfaces,DSP, and memory that are coupled over bus circuitry. The antennas in UE401 are wirelessly coupled to EN-DC access node 411 over one or moreradio bands. User circuitry 404 comprises user interfaces (IF), CPU, andmemory. The memory in user circuitry 404 stores an operating system,user applications, and network applications for PHY, MAC, RLC, PDCP, andRRC. The CPU executes the operating system, user applications, andnetwork applications to exchange signaling and data between the userapplications and the RRC and PDCP. The CPU executes the operating systemand network applications to wirelessly exchange corresponding signalingand data with EN-DC access node 411 over radios 402-403.

In radios 402-403, the antennas receive wireless signals from EN-DCaccess node 411 that transport DL signaling and DL data. The antennastransfer corresponding electrical DL signals through duplexers to theamplifiers. The amplifiers boost the received DL signals for filterswhich attenuate unwanted energy. In modulation, demodulatorsdown-convert the DL signals from their frequency bands. Theanalog/digital interfaces convert the analog DL signals into digital DLsignals for the DSPs. The DSPs recover DL symbols from the DL digitalsignals. The CPU executes the network applications to process the DLsymbols and recover the DL signaling and DL data. The RRC transferscorresponding DL user signaling to the operating system/userapplications. The PDCP transfers corresponding DL user data to theoperating system/user applications.

The PDCP receives UL user data from the operating system/userapplications. The RRC receives UL signaling from the operatingsystem/user applications. The RRC processes the UL signaling and the DLsignaling to generate new DL signaling and new UL signaling. The networkapplications process the UL signaling and the UL data to generatecorresponding UL symbols. In radios 402-403, the DSPs process the ULsymbols to generate corresponding digital signals for theanalog-to-digital interfaces. The analog-to-digital interfaces convertthe digital UL signals into analog UL signals for modulation. Modulationup-converts the UL signals to their frequency bands. The amplifiersboost the modulated UL signals for the filters which attenuate unwantedout-of-band energy. The filters transfer the filtered UL signals throughduplexers to the antennas. The electrical UL signals drive the antennasto emit corresponding wireless signals that transport the UL signalingand UL data to EN-DC access node 411.

RRC functions comprise authentication, security, handover control,status reporting, Quality-of-Service (QoS), network broadcasts andpages, and network selection. SDAP functions comprise QoS marking andflow control. PDCP functions comprise LTE/5GNR allocations, securityciphering, header compression and decompression, sequence numbering andre-sequencing, de-duplication. RLC functions comprise Automatic RepeatRequest (ARQ), sequence numbering and resequencing, segmentation andresegmentation. MAC functions comprise buffer status, power control,channel quality, Hybrid Automatic Repeat Request (HARM), useridentification, random access, user scheduling, and QoS. PHY functionscomprise packet formation/deformation, windowing/de-windowing,guard-insertion/guard-deletion, parsing/de-parsing, controlinsertion/removal, interleaving/de-interleaving, Forward ErrorCorrection (FEC) encoding/decoding, rate matching/de-matching,scrambling/descrambling, modulation mapping/de-mapping, channelestimation/equalization, Fast Fourier Transforms (FFTs)/Inverse FFTs(IFFTs), channel coding/decoding, layer mapping/de-mapping, precoding,Discrete Fourier Transforms (DFTs)/Inverse DFTs (IDFTs), and ResourceElement (RE) mapping/de-mapping.

Before a handover from EN-DC access node 411 to a target access node(not shown), the RRC in UE 401 receives measurement object specificoffsets from EN-DC access node 411. The offsets include a serving celloffset for EN-DC access node 411, neighbor cell offsets for neighboraccess nodes, and neighbor frequency offsets for the neighbor accessnodes. The serving cell offset represents and/or indicates the ULinterference at EN-DC access node 411 for the radio band used by UE 401.Thus, the serving cell offset accelerates handovers when UL interferenceis high and decelerates handovers when the UL interference is low.

In UE 401, the PHY determines DL signal strengths for EN-DC access node411 and for the neighbor access nodes—typically during channelestimation. The PHY notifies the RRC of the DL signal strengths. The RRCprocesses the DL signal strengths, offsets, and hysteresis values totrigger a handover to one of the neighbor access nodes—the target accessnode. In particular, the RRC determines when a sum of the DL signalstrength for EN-DC access node 411, the serving cell offset (maybe anegative value), and a hysteresis value fall below an A5-1 threshold.When the A5-1 threshold triggers, the RRC determines when a sum of theDL signal strength, the neighbor cell offset, the neighbor frequencyoffset, and a hysteresis value exceed an A5-2 threshold for the targetaccess node. When the A5-2 threshold triggers, the RRC transfers thehandover request to EN-DC access node 411. The handover requestindicates the DL signal strength at UE 401 for EN-DC access node 411,the target access node, and some of the other neighbor access nodes. TheRRC exchanges handover signaling with EN-DC access node 411 and with thetarget access node to perform the handover. After the handover, the RRC,PDCP, RLC, MAC, and PHY exchange data and signaling with the targetaccess node.

FIG. 5 illustrates EN-DC access node 411 to handover wireless UE 401 inresponse to UL interference. EN-DC access node 411 is an example ofcells 111-112, although cells 111-112 may differ. EN-DC access node 411comprises 5GNR radios 412, LTE radios 413, 5GNR Baseband Unit (BBU) 414,and LTE BBU 415. Radios 412-413 comprise antennas, amplifiers, filters,modulation, analog-to-digital interfaces, DSP, and memory that arecoupled over bus circuitry. BBUs 414-415 comprises memory, CPU, and dataInput/Output (I/O) that are coupled over bus circuitry.

UE 401 is wirelessly coupled to the antennas in radios 412-413. Radios412-413 and BBUs 414-415 are coupled over data links like Common PublicRadio Interface (CPRI) or some other network protocol. The data I/Os inBBUs 414-415 are coupled over backhaul links to MME 421 and SAE GW 422in NFVI 420. In BBUs 414-415, the memories store operating systems (OS),Physical Layers (PHY), Media Access Controls (MAC), Radio Link Controls(RLC), Packet Data Convergence Protocols (PDCP), and Radio ResourceControls (RRC). The CPU executes the PHY, MAC, RLC, PDCP, and RRC todrive the exchange of data and signaling between UE 401 and NFVI 420over radios 412-413.

In radios 412-413, the antennas receive wireless signals from UE 401that transport UL signaling and UL data. The antennas transfercorresponding electrical UL signals through duplexers to the amplifiers.The amplifiers boost the received UL signals for filters which attenuateunwanted energy. In modulation, demodulators down-convert the UL signalsfrom the their frequency bands. The analog/digital interfaces convertthe analog UL signals into digital UL signals for the DSP. The DSPrecovers UL symbols from the UL digital signals. In BBUs 414-415, theCPUs execute the network applications to process the UL symbols andrecover UL LTE signaling, UL LTE data, and UL 5GNR data. In LTE BBU 415,the CPU executes the RRC to process the UL LTE signaling and DL LTEsignaling to generate new UL LTE signaling and new DL LTE signaling. TheRRC transfers the new UL LTE signaling to MME 421 in NFVI 420 over thedata I/O and backhaul links. The PDCP transfers the UL LTE data to SAEGW 422 over the data I/O and backhaul links. In 5GNR BBU 414, the PDCPtransfers the UL 5GNR data to SAE GW 422 over the data I/O and backhaullinks.

In LTE BBU 415, the RRC receives DL LTE signaling from MME 421, and thePDCP receives DL LTE data from SAE GW 422 over the data I/O and thebackhaul links. The CPU executes the network applications to process theDL LTE signaling, DL LTE data to generate corresponding DL symbols thatrepresent the DL signaling and DL data in the frequency domain. In 5GNRBBU 414, the PDCP receives DL 5GNR data from SAE GW 422 over the dataI/O and the backhaul links. The CPU executes the network applications toprocess the DL 5GNR data to generate corresponding DL symbols thatrepresent the DL data in the frequency domain.

In radios 412-413, the DSP processes the DL symbols to generatecorresponding digital signals for the analog-to-digital interfaces. Theanalog-to-digital interfaces convert the digital DL signals into analogDL signals for modulation. Modulation up-converts the DL signals totheir frequency bands. The amplifiers boost the modulated DL signals forthe filters which attenuate unwanted out-of-band energy. The filterstransfer the filtered DL signals through duplexers to the antennas. Theelectrical DL signals drive the antennas to emit corresponding wirelesssignals that transport the DL signaling and DL data to UE 401.

RRC functions comprise authentication, security, handover control,status reporting, QoS, network broadcasts and pages, and networkselection. PDCP functions comprise LTE/5GNR allocations, securityciphering, header compression and decompression, sequence numbering andre-sequencing, de-duplication. RLC functions comprise ARQ, sequencenumbering and resequencing, segmentation and resegmentation. MACfunctions comprise buffer status, power control, channel quality, HARQ,user identification, random access, user scheduling, and QoS. PHYfunctions comprise packet formation/deformation, windowing/de-windowing,guard-insertion/guard-deletion, parsing/de-parsing, controlinsertion/removal, interleaving/de-interleaving, FEC encoding/decoding,rate matching/de-matching, scrambling/descrambling, modulationmapping/de-mapping, channel estimation/equalization, FFTs/IFFTs, channelcoding/decoding, layer mapping/de-mapping, precoding, DFTs/IDFTs, and REmapping/de-mapping.

For handovers of wireless UE 401 from EN-DC access node 411 to targetaccess nodes, the PHYs determine UL interference power during channelestimation for the radio band used by UE 401. The PHYs signal the ULinterference power level to the RRC. In LTE BBU 415, the RRC generates aserving cell offset that indicates the UL interference measured by thePHYs for the radio band. The serving cell offset is typically a negativedecibel value. The RRC transfers measurement object specific offsets(serving cell offset, neighbor cell offsets, and neighbor frequencyoffsets) to the RRC in UE 401.

Advantageously, the serving cell offset represents and/or indicates theUL interference at EN-DC access node 411. The serving cell offsetaccelerates handovers when UL interference is high and decelerateshandovers when UL interference is low. In LTE BBU 415, the RRC receivesa handover request from UE 401 that indicates the DL signal strength atUE 401 for EN-DC access node 411 and at least one neighbor access node.The RRC verifies that the sum of the DL signal strength for EN-DC accessnode 411, the serving cell offset, and the hysteresis value fall belowthe A5-1 threshold and that the sum of the DL signal strength for thetarget neighbor access node, the neighbor cell offset, the neighborfrequency offset, and the hysteresis value exceed the A5-2 threshold.When the A5 handover triggers are verified, the RRC transfers handoversignaling to the target access node, UE 401, and MME 421. After thehandovers, EN-DC access node 411 does not exchange data with UE 401(until UE 401 may subsequently reattach to access node 401).

On handovers of UE 401 from a serving access node (not shown) to EN-DCaccess node 411, the RRC in LTE BBU 415 receives handover signaling fromthe serving access node for UE 401. In response, the RRC transfershandover signaling to the serving access node, UE 401, and MME 421.After the handover, the RRC, PDCP, RLC, MAC, and PHY exchange data andsignaling with UE 401 over radios 412-413. The RRC and PDCP exchangecorresponding signaling and data with MME 421 and SAE GW 422 overbackhaul links.

In some examples, the RRC in LTE BBU 415 averages the UL interferencepower over time to generate average UL interference values at EN-DCaccess node 411 over the radio bands for various days, date, and times.The RRC then processes the historical UL interference averages for thecurrent day, date, time, and radio band to generate a neighbor frequencyoffset that is based on the historical UL interference power for thetime, day, and date for the radio band. The RRC transfers the neighborfrequency offsets for the radio bands of EN-DC access node 411 to theneighbor access nodes. The neighbor access nodes transfer the neighborfrequency offsets for their radio bands to their served UEs. The UEs usethe neighbor cell offsets to trigger handovers to EN-DC access node 411based on historical UL interference at EN-DC access node 411. The UEsmay also use serving cell offsets that indicate actual UL interferenceat the serving access node. The neighbor frequency offset decelerateshandovers when historical UL interference is high and accelerateshandovers when historical UL interference is low.

FIG. 6 illustrates Network Function Virtualization Infrastructure (NFVI)420 to support the handover of UE 401 in response to UL interference atthe serving EN-DC access node 411. NFVI 420 is an example of networkelements 121, although network elements 121 may differ. NFVI 420comprises hardware 621, hardware drivers 622, operating systems andhypervisors 623, virtual layer 624, and Virtual Network Functions (VNFs)625. Hardware 621 comprises Network Interface Cards (NICs), CPUs, RAM,flash/disk drives, and data switches (SWS). Virtual layer 624 comprisesvirtual NICs (vNIC), virtual CPUs (vCPU), virtual RAM (vRAM), virtualDrives (vDRIVE), and virtual Switches (vSW). The NICs in NFVI 420 arecoupled to EN-DC access node 411 and neighbor access nodes over backhaullinks. VNFs 425 comprise MME 421, SAE GW 422, and other VNFs. Hardware621 executes hardware drivers 622, operating systems and hypervisors623, virtual layer 624, and VNFs 625 to serve UE 401 with data servicesover EN-DC access node 411.

MME 421 receives handover signaling for UE 401 from the serving accessnode (EN-DC access node 411 or one of its neighbor access nodes). Inresponse, MME 421 signals SAE GW 422 to terminate the existing databearer for UE 401 through the serving access node. MME 421 signals theserving access node to terminate the data bearer for UE 401 and todirect UE 401 to attach to the target access node. In response, MME 421signals SAE GW 422 and the target access node to add a new data bearerfor UE 401 through the target access node (EN-DC access node 411 or oneof its neighbor access nodes).

FIG. 7 illustrates the operation of EN-DC communication network 400 tohandover UE 401 in response to UL interference at EN-DC access node 411.On a handover of UE 401 from EN-DC access node 411 to a target, the PHYsin node 411 determine UL interference power during channel estimationfor the radio band used by UE 401. The PHYs signal the UL interferencepower level to the RRC. The RRC generates a serving cell offset thatindicates the UL interference power on the radio band used by the UE.The RRC in EN-DC access node 411 transfers the serving cell offset,neighbor cell offsets, and neighbor frequency offsets to the RRC in UE401. The neighbor frequency offsets may represent historical ULinterference at the neighbor access nodes for the current day, date,time, and band. In UE 401, the RRC receives the offsets from EN-DCaccess node 411. The PHYs in UE 401 determine DL signal strength overthe radio bands used by EN-DC access node 411 and the neighbor accessnodes—typically during channel estimation. The PHYs notify the RRC in UE401 of the DL signal strengths. The RRC in UE 401 determines when a sumof the DL signal strength at UE 401 for EN-DC access node 411, theserving cell offset for the band, and a hysteresis value falls below anA5-1 threshold. When the A5-1 threshold triggers, the RRC in UE 401determines when a sum of the DL signal strength for the target, theneighbor cell offset, the neighbor frequency offset, and a hysteresisvalue exceed an A5-2 threshold. When the A5-2 threshold triggers, theRRC transfers the handover request to EN-DC access node 411. Thehandover request indicates the DL signal strength at UE 401 for EN-DCaccess node 411, the target access node, and some of the other neighboraccess nodes. In EN-DC access node 411, the RRC receives the handoverrequest from UE 401. The RRC verifies A5-1 and A5-2 triggers. When theA5-1 and A5-2 triggers are verified, the RRC transfers handoversignaling to the RRC in the target access node and to MME 421 in NFVI420. MME 421 signals SAE GW 422 to terminate the existing data bearersfor UE 401 through EN-DC access node 411. MME 421 signals the RRC inEN-DC access node 411 to terminate the data bearers for UE 401. MME 421signals the RRC in EN-DC access node 411 to direct UE 401 to attach tothe target access node, and the RRC in in EN-DC access node 411 signalsUE 401 to attach to the target access node. The RRC in UE 401 attachesto the target access node. EN-DC access node 411 forwards downlink datato the target access node. MME 421 signals SAE GW 422 and the RRC in thetarget access node to add new data bearers for UE 401. UE 401 thenexchanges data with SAE GW 422 over the target access node instead ofEN-DC access node 411. SAE GW 422 exchanges the data with other datasystems to deliver the data service.

For a handover of UE 401 from a source to EN-DC access node 411, thePHYs in node 411 determine UL interference power during channelestimation for the radio band used by UE 401. The PHYs signal the ULinterference power levels to the RRC. The RRC generates a neighborfrequency offset for the radio band based on the historical ULinterference data for the current day, date, and time. The RRC in EN-DCaccess node 411 transfers the neighbor cell offset to the RRCs in theneighbor access nodes. The RRCs in the neighbor access nodes transferthe neighbor offset for the radio band to UE 401. The PHYs in UE 401determine DL signal strength for the serving access node, EN-DC accessnode 411, and other neighbor access nodes—typically during channelestimation. The PHYs notify the RRC in UE 401 of the DL signalstrengths. The RRC in UE 401 determines when a sum of the DL signalstrength for the serving access node, the serving cell offset (which isbased on actual UL interference at the serving access node), and ahysteresis value fall below the A5-1 threshold. When the A5-1 thresholdtriggers, the RRC in UE 401 determines when a sum of the DL signalstrength for the EN-DC access node 411, the neighbor cell offset, theneighbor frequency offset (which is based on historical UL interferenceat EN-DC access node 411 for the radio band), and a hysteresis valueexceed an A5-2 threshold. When the A5-2 threshold triggers, the RRCtransfers the handover request to the serving access node. The handoverrequest indicates the DL signal strength at UE 401 for the servingaccess node, EN-DC access node 411, and some of the other neighboraccess nodes. The serving access node verifies the A5 triggers transfershandover signaling to the RRC in EN-DC access node 411 and to MME 421 inNFVI 420. MME 421 signals SAE GW 422 to terminate the existing databearers for UE 401 through the serving access node. MME 421 signals theRRC in the serving access node to terminate the data bearers for UE 401.MME 421 signals the RRC in the serving access node to direct UE 401 toattach to EN-DC access node 411, and the RRC in the target access nodesignals UE 401 to attach to EN-DC access node 411. The RRC in UE 401attaches to EN-DC access node 411. The target access node forwardsdownlink data to EN-DC access node 411. MME 421 signals SAE GW 422 andthe RRC in EN-DC access node 411 to add new data bearers for UE 401. UE401 then exchanges data with SAE GW 422 over EN-DC access node 411instead of the target access node. SAE GW 422 exchanges the data withother data systems to deliver the data service.

The wireless data network circuitry described above comprises computerhardware and software that form special-purpose network circuitry tohandover wireless UEs between wireless access nodes responsive to uplinkinterference power. The computer hardware comprises processing circuitrylike CPUs, DSPs, GPUs, transceivers, bus circuitry, and memory. To formthese computer hardware structures, semiconductors like silicon orgermanium are positively and negatively doped to form transistors. Thedoping comprises ions like boron or phosphorus that are embedded withinthe semiconductor material. The transistors and other electronicstructures like capacitors and resistors are arranged and metallicallyconnected within the semiconductor to form devices like logic circuitryand storage registers. The logic circuitry and storage registers arearranged to form larger structures like control units, logic units, andRandom-Access Memory (RAM). In turn, the control units, logic units, andRAM are metallically connected to form CPUs, DSPs, GPUs, transceivers,bus circuitry, and memory.

In the computer hardware, the control units drive data between the RAMand the logic units, and the logic units operate on the data. Thecontrol units also drive interactions with external memory like flashdrives, disk drives, and the like. The computer hardware executesmachine-level software to control and move data by driving machine-levelinputs like voltages and currents to the control units, logic units, andRAM. The machine-level software is typically compiled from higher-levelsoftware programs. The higher-level software programs comprise operatingsystems, utilities, user applications, and the like. Both thehigher-level software programs and their compiled machine-level softwareare stored in memory and retrieved for compilation and execution. Onpower-up, the computer hardware automatically executesphysically-embedded machine-level software that drives the compilationand execution of the other computer software components which thenassert control. Due to this automated execution, the presence of thehigher-level software in memory physically changes the structure of thecomputer hardware machines into special-purpose network circuitry tohandover wireless UEs between wireless access nodes responsive to uplinkinterference power.

The above description and associated figures teach the best mode of theinvention. The following claims specify the scope of the invention. Notethat some aspects of the best mode may not fall within the scope of theinvention as specified by the claims. Those skilled in the art willappreciate that the features described above can be combined in variousways to form multiple variations of the invention. Thus, the inventionis not limited to the specific embodiments described above, but only bythe following claims and their equivalents.

What is claimed is:
 1. A method of operating a wireless communicationnetwork to handover wireless User Equipment (UE) from a serving cell toa neighbor cell, the method comprising: the serving cell wirelesslyexchanging data with the wireless UE over a serving radio band; theserving cell determining uplink interference at the serving cell for theserving radio band and determining an average uplink interference valueat the neighbor cell for a different radio band; the serving cellwirelessly transferring an uplink interference offset to the wireless UEthat indicates the uplink interference at the serving cell for theserving radio band and the average uplink interference value at theneighbor cell for the different radio band, wherein the wireless UE usesthe uplink interference offset to trigger a handover request to theserving cell that indicates downlink signal strength at the wireless UEfor the serving cell and the serving radio band and another downlinksignal strength at the wireless UE for the neighbor cell and thedifferent radio band; the serving cell initiating a handover to aneighbor cell responsive to a combination of the downlink signalstrength at the wireless UE and the uplink interference for the servingcell falling below a handover threshold and to another combination ofthe other downlink signal strength at the wireless UE for the neighborcell and the average uplink interference value at the neighbor cell forthe different radio band exceeding another handover threshold; and theneighbor cell wirelessly exchanging additional data with the wireless UEafter the handover.
 2. The method of claim 1 wherein the handoverthreshold comprises a Fifth Generation New Radio (5GNR) A5-1 threshold.3. The method of claim 1 wherein the handover threshold comprises a LongTerm Evolution (LTE) A5-1 threshold.
 4. The method of claim 1 whereinthe serving cell initiating the handover to the neighbor cell responsiveto the combination of the downlink signal strength and the uplinkinterference for the serving cell falling below the handover thresholdcomprises initiating the handover to the neighbor cell responsive to acombination of the downlink signal strength, the uplink interference,and a hysteresis value for the serving cell falling below the handoverthreshold.
 5. The method of claim 1 wherein the uplink interferenceoffset comprises a measurement object specific offset for the servingcell.
 6. The method of claim 1 wherein the uplink interference offsetaccelerates the handover when the uplink interference has increased anddecelerates the handover when the uplink interference has decreased. 7.The method of claim 1 wherein the handover comprises an inter-bandhandover from the radio band to the different radio band.
 8. The methodof claim 1 wherein the average uplink interference value at the neighborcell comprises a measurement object specific offset for the neighborcell.
 9. A wireless communication network to handover wireless UserEquipment (UE) from a serving cell to a neighbor cell, the wirelesscommunication network comprising: the serving cell configured towirelessly exchange data with the wireless UE over a radio band,determine uplink interference at the serving cell for the radio band,determine an average uplink interference value at the neighbor cell fora different radio band, and wirelessly transfer an uplink interferenceoffset to the wireless UE that indicates the uplink interference at theserving cell for the radio band and the average uplink interferencevalue at the neighbor cell for the different radio band, wherein thewireless UE is configured to use the uplink interference offset totrigger a handover request to the serving cell that indicates downlinksignal strength at the wireless UE for the serving cell and anotherdownlink signal strength at the wireless UE for the neighbor cell; theserving cell configured to initiate a handover to a neighbor cellresponsive to a combination of the downlink signal strength at thewireless UE and the uplink interference for the serving cell fallingbelow a handover threshold and to another combination of the otherdownlink signal strength at the wireless UE and the average uplinkinterference value for the neighbor cell exceeding another handoverthreshold; and the neighbor cell configured to wirelessly exchangeadditional data with the wireless UE after the handover.
 10. Thewireless communication network of claim 9 wherein the handover thresholdcomprises a Fifth Generation New Radio (5GNR) A5-1 threshold.
 11. Thewireless communication network of claim 9 wherein the handover thresholdcomprises a Long Term Evolution (LTE) A5-1 threshold.
 12. The wirelesscommunication network of claim 9 wherein the serving cell is configuredto initiate the handover to the neighbor cell responsive to acombination of the downlink signal strength, the uplink interference,and a hysteresis value for the serving cell falling below the handoverthreshold.
 13. The wireless communication network of claim 9 wherein theuplink interference offset comprises a measurement object specificoffset for the serving cell.
 14. The wireless communication network ofclaim 9 wherein the uplink interference offset will accelerate thehandover when the uplink interference is increased and decelerate thehandover when the uplink interference is decreased.
 15. The wirelesscommunication network of claim 9 wherein the handover comprises aninter-band handover from the radio band to the different radio band. 16.The wireless communication network of claim 9 wherein the average uplinkinterference value at the neighbor cell comprises a measurement objectspecific offset for the neighbor cell.